LU-8703 libcfs: rework CPU pattern parsing code

LU-8703 libcfs: rework CPU pattern parsing code

Rewrite CPU pattern parsing code to avoid passed buffer change
add real errors propogation to caller function.

Change-Id: I8dfee2c0013fcfccd3d99c361d3ec626594689bd
Signed-off-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-on: https://review.whamcloud.com/23306
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Patrick Farrell <paf@cray.com>
Reviewed-by: Olaf Weber <olaf.weber@hpe.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>